L4

Question 1

transforming principle

Answer 1

a substance in the heat killed s cells caused a heritable change of a non-virulent r bacteria into virulent s bacteria

Question 2

What is DNA

Answer 2

a polymer of nucleotides linked by phosphodiester bonds

Question 3

what are the nucleotides of dna?

Answer 3

5c sugar, purines (a and g), pyrimidines (t, u , c)

Question 4

What type of molecule is dna?

Answer 4

dna is a polar molecule

phospodiester bond creates polarity

Question 5

What is the directionality of DNA?

Answer 5

(polar) 5’ –> 3’

5’ phosphate
3’ hydroxly

Question 6

what is the backbone

Answer 6

pentose-phospate units

Question 7

Dna double helix features

Answer 7

complementary, antiparallel, right handed

Question 8

What is the primary structure?

Answer 8

linked nucleotides

Question 9

What is the 3D structure satablized by?

Answer 9

non-covalent bonds

Question 10

what is the base parining anf base staking?

Answer 10

hydrogen bonds and van der waals and hydrophobic bonds (the aromatic ring)

Question 11

What is the relaxed and supercoil of DNA? (topology)

Answer 11

dna twisted upon itself

Question 12

what is the function of supercoiling

Answer 12

negative - enahcnes accesbillity
positive - tighter winding recudes access

Question 13

What do topoimerases do?

Answer 13

catalyze the relaxation of supercoiled dna

Question 14

What is topomerase TYPE I?

Answer 14

transiet single strand cut

Question 15

what is topomerase TYPE II?

Answer 15

transiet double strand cut

Question 16

What feature of the DNA
structure explains the Chargaff’s
rules?

Answer 16

complementary base pairing

Question 17

how does dna packaging work in prokaryotes?

Answer 17

supercoiled

naked - not associated with histonen proteins

Question 18

how does dna packaging work in eukaryotes?

Answer 18

Chromatin, dynamic structure, chromosome

Question 19

what is chromatin?

Answer 19

dna + proteins (histone and non-histone proteins)

Question 20

what are histones?

Answer 20

proteins essential fo rdna packaging, organization, and regulation in eukaryotic cells

back bone of chromatin

Question 21

interphase (chromatin)

Answer 21

disperesed/relaxed structure of chromatin packaging

Question 22

mitosis (chromatin)

Answer 22

condensed/compacted –> metaphsic chromosomes

Question 23

what is a chromosome?

Answer 23

one large dna molecule

Question 24

what is beads-on-string?

Answer 24

nucleosome + linker dna

relaxed/opne - transcriptionally active
h
highly structural packaging - no active transport

Question 25

what are histones?

Answer 25

histones are the main protein involved in packaging

Question 26

what is the function of histones?

Answer 26

dna compaction and regulation of gene expressing

Question 27

what are some histone variants?

Answer 27

cenp-a histones that are only found in centromere

Question 28

what are n-terminal tails?

Answer 28

targets for posttranslational modifications such as acetylation, methylation, and phosphorylation

Question 29

Nucleosome structure

Answer 29

the structural unitls of chromatin

Question 30

function of nucleosomes?

Answer 30

regulate dna packaging and access

Question 31

what does the histone core (octamer) look like?

Answer 31

n-tails projected outward

Question 32

where is linker dna?

Answer 32

between nulceosomes

Question 33

Interphase states (chromatin in the cell cycle)

Answer 33

euchromatin , heterchormatin

Question 34

what is euchromatin ?

Answer 34

active transport , beads-on-string (open , extended)

Question 35

what is heterochromatin ?

Answer 35

no transcription

Question 36

faculative

Answer 36

can be converted into euchromatin

Question 37

constitiutive

Answer 37

centromeres and telomeres

Question 38

mitosis and meiosis (chromatin in the cell cycle

Answer 38

Gradual condensation in prophase Metaphase – maximal compaction

Question 39

Why do eukaryotes need histones, whereas prokaryotes do not?

Answer 39

Histones are needed to compact the very long DNA molecules in eukaryotes.

Question 40

Features of the regulation of chromatin condensation

Answer 40

ATP dependant nucleosome sliding - repostion of nucleosomes (increases/reduces access to dna

Question 41

what does histone modifications?

Answer 41

n-terminus tails of core histones PTM - acetylation, methylation, phosphorylation, and ubiquitinylation Regulate chromosome structure (condensation) → function

Question 42

What is acetylation?

Answer 42

looser packaging

Question 43

what is methylation?

Answer 43

tighter packaging

Question 44

Interphase (chromosomes)

Answer 44

territories , restricted regions chromatin - organized into non-overlapping territories in the nucleus

Question 45

what are metaphasic chromosomes?

Answer 45

visible in light microscope high level of condestion karyotype - number, size, shape

Question 46

what is polyplodiy and aneuploidy?

Answer 46

poly - extra set of chromosomes aneu - extra or missing one copy of chromosmes

Question 47

Origin of replication in prokaryotes and eukaryotes

Answer 47

Pro - single origin Euk - multiple

Question 48

what does the centromere sequence do?

Answer 48

Specialized repetitive DNA regions Centromere specific histone H3 (CENP-A) Assemble kinetochore proteins Attach to spindle microtubules Ensures proper chromosome segregation during divisio

Question 49

Telomere sequences

Answer 49

TTAGGG repeats (humans) protects ends from deradation

Question 50

Non-repeated DNA

Answer 50

single copy genes encode protein s functional RNA (rRNA, miRNA...) Regulatory sequences ( promoters, enhancers)

Question 51

Repeated DNA

Answer 51

tandemly repeated associated with: huntingtons, fragile x syndrome..

Question 52

The centromere is a region on the chromosome where two sister chromatids are attached during prophase and metaphase of mitosis. However, the centromere ”disappears” when the sister chromatids separate at anaphase. How is that region of the chromosome marked so that the cell knows where the centromere should be placed in the next round of mitosis

Answer 52

CENP-A histones are used to mark where the centromere should be.

Question 53

Why do chromosomes require telomeres?

Answer 53

to protect chromosome ends from degradation